It's easier than it sounds. You just have to think rightly about the various issues.
is measured in lumens. In a closed small space like a room, this works out to be a fairly absolute unit. 1000 lumens is about the same amount of light, whether it's coming from an Edison bulb or a LED strip. That's not the whole picture, but the considerations are fairly obvious, e.g. is the light near your workspace, is it "bounce light" etc.
(on the other hand, when dealing with light traveling a long distance, e.g. a headlight, then you get into a lot of complicated geometry and optics and units like candela. You don't need to deal with that in a closed space like a room.)
Light spectrum and "Whiteness"
Color Temperature describes the color of the light. 2700K is a traditional yellowish incandescent. 3000K is halogen. 4100K is traditional fluorescent. 5000K is modern fluorescent, and it gets bluer from there. Higher numbers seem brighter and are great for task lighting, say, in your workshop... but for aesthetic reasons, you will want a warmer (yellower, lower) color temp in the more "homey" parts of your home. Seriously. 5000K sounds great in the showroom, but you'll end up tearing it out.
Next is CRI, or Color Rendering Index. That is the thing that really bothers people about bad lighting - remember those very yellow street lights, which had a CRI of about 15? 100 CRI is perfect. 80 CRI is readily available, and >90 CRI is available with a bit of hunting.
LED production is a bit of a dice roll. Manufacturers never quite know how a batch will come out, so they test and grade (bin, verb) by color temp and CRI. You'll see the bins discussed on LED datasheets. They get top dollar for the most desirable color temps and CRI's. The least desirable bins get dumped to the LED strip makers you find on eBay. If they don't state CRI, it's because they're taking the leftovers and don't know what they're going to get.
Lumens, color temperature and CRI are used for all lamps of all kinds. Nowadays you should be using lumens, not "watts", to pick bulb brightness. "60 watt equivalent" is marketing bull; lumens are an accurate number.
Uneven light and Positioning
LED strips have emitters at a certain spacing. This is completely obvious the moment you turn one on. LEDs emit a great deal of light from a tiny spot, which can be disturbing. Obviously, you have to deal with that in your design. Cove lights or other bounce lighting are perfect for diffusing LED light.
It really helps that unlike any other bulb, LEDs emit light in a cone of about 140 degrees. So you can aim the light where you want it, and don't waste light where you don't.
tell you what kind of power the LEDs require. From here on out, I'm going to talk about a 12V strip (which by design has 3 LEDs in series). A 24V strip has 6 LEDs in series, so current will be 50% typically.
A 3528 device has 1 channel or color, with 2 wires total, + and -. On a 12V strip, 300 LEDs draw 2 amps. That's the handy math to remember. I've tried doing the math other ways, but this is the simplest.
Suppose you have a half-density, 150 LED per 5 metre strip. Half the LEDS = half the amps,
1A. A double-density 600-LED strip takes 4A. Etc. You cut a strip to half length, half the amps.
Suppose you have a standard 5-metre, 600-LED strip (that's double the 300, so 4A per 5 metres). But you are using 2 metres of it, or 2/5 of the strip. That's
4A * 2/5 = 1.6 amps.
A 5050 device has 3 channels. Often 3 different colors, but sometimes 3 of the same color, typically a white. 300 LEDs draw 2 amps per channel, 3 channels. The same multiplying and dividing rules apply.
For instance, the common 300-LED RGB strip with 5050s. It has 3 channels - R G B. How much power does it take? 2 amps per channel, 6 amps whole-strip. Easy peasy. Now, what about the return/common wire? Oh, that takes the full 6 amps.
For instance, suppose we have a RGBW combo strip that has 300 5050's. Except half of them, 150, are RGB LEDs. How many amps do those take? Correct, there are 150 of them, so they take 1 amp per channel, or 3 amps in combo. Then it also has 150 WWW LEDs (white-white-white), and all 3 of those channels are wired together. How much current do those take? Same math, but all 3 wired together, so it takes 3 amps for that channel. See how that worked out? The common return is a whopping 6 amps.
What do those numbers mean? A 5050 LED package is 5.0mm x 5.0mm. A 3528 is 3.5mm x 2.8mm. That's all.
An LED-strip "controller" is simply an LED-strip dimmer that dims R, G and B channels independently, yielding millions of colors. You cannot use any random dimmer with LED strips. ** Dimming and color-blending are done by PWM (pulse-width modulation). *** The LED turns on and off very rapidly - thousands of times a second, far too fast to see. The percentage of "on" vs "off" decides how bright it is. (this is called duty cycle).
Since PWM is hard on/off, it's digital and it can be copied accurately. That's what an amplifier does. It pulses power to its own LEDs, but it uses the controller/dimmer as a pilot signal. As such, it pulses the same, and yields the same brightness. So if you have an 8A controller, you can use that to drive a 6A LED strip, and also an amplifier driving another 12A of LED strip. This all works.
A possible amplifier configuration, here with RGBW strips which have 4 channels instead of 3. Black is common.
Noise from power supplies and Waterproof
This is not a common problem, and it's easy to make power supplies silent. If you can hear your power supply, get a better power supply. Waterproofness has nothing to do with loudness. Some power supplies have fans, obviously those are not silent. Nothing about noise makes it any safer.
If you use LEDs indoors, IP ratings are irrelevant, except water-resistant LEDs are easier to dust. However the water shielding will yellow or get cloudy long before the LED wears out, and will be the limiting factor in LED life. Outdoors, on the eBay cheapies, don't expect long life out of the waterproof coatings, maybe a year.
** In fact, it is a sad cliche where consumers want certain functionality, so they randomly pick products off the shelf at the big-box store, and expect them to work together even though they are not listed to work together. Don't do that. Anytime products need to work together (you know, like a lamp and a dimmer), make sure they are designed to work together.
*** You must not use PWM to "dim" consumer-packaged LED products such as screw-in bulb replacements, driving lights etc. because they have their own internal smart power supply. That power supply will defeat the dimming, treating it as a power quality problem and compensating by drawing more power to keep its light on at full power. This can overload things. So, for instance, if you have your dimming LED strip system, and you see some nice 12V IKEA spot lights you'd like to add to the system, ask or study a teardown to see if that lamp is compatible with PWM dimming. (i.e. it contains only LED emitters and resistors).